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How could nothing is finite yet unbounded?

  1. Jan 14, 2014 #1
    Hey guys. It's been awhile I don't posting in this thread.

    How could space which is nothing, is finite yet unbounded? Aren't beyond the so-called finite yet unbounded universe is just nothing that we called as space?
  2. jcsd
  3. Jan 14, 2014 #2


    Staff: Mentor

    The surface of a sphere is finite but unbounded.

    Given the radius you can determine the surface area of the sphere (finite).

    You can traverse it any way you want and you won't find a boundary (unbounded).
  4. Jan 14, 2014 #3
    The boundaries are between the surface and the interior on the one hand, and between the surface and its exterior surroundings on the other.
  5. Jan 14, 2014 #4


    Staff: Mentor

    Thats if you consider it as a 3D object. I'm using the exterior surface of the sphere only.
  6. Jan 15, 2014 #5


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    An illustration of that is our choice of starting longitude coordinate: it is completely arbitrary because there is no boundary to constrain your motion along the surface of the earth.
  7. Jan 15, 2014 #6
    But space is not an object with shape and location. How could we say space is finite but yet unbounded? In my opinion, space is of course non-finite but it is also non-infinite because space which is nothing, can't be said as finite or infinite because these terms imply size. Only objects have size.
  8. Jan 15, 2014 #7


    Staff: Mentor

    You can extend the sphere concept into the hypersphere where its surface is like 3D space. In this space you can travel in any direction and come back to where you started but never hit a boundary.

    If our universe was like this then light leaving the earth would eventually come back to earth once more if nothing deflected or absorbed it on the journey.

  9. Jan 15, 2014 #8


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    Look up Mobius Strip and Klein Bottle. They, also, are hard to get your head round.
  10. Jan 15, 2014 #9
    Assuming you mean "the vacuum of outer space," space is far from nothing.
    All sections of space have a temperature, significant photon flux, etc.
  11. Jan 15, 2014 #10

    Perhaps you could help us to answer your question by telling us more.
    "How could space,* which is nothing, be* finite and* unbounded"
    First of all, where did you hear this quote? It looks to me like you have seen/heard/viewed two or three different theories and asked how they can all be correct.

    Secondly, nobody has been to the edge of space (as far as I know,lol) nor has anyone shot a beam of light in one direction and the beam return in the opposite. Because of this, nobody can provide a straightforward answer. We can however, provide theories explaining some things. Everytime I post a theorie (not of my own) I get an email that bans me from the forums. I will have to leave the theories explaining your question to others (the moderators).

    What stumps me on this question is, if there is an edge to the universe, whats past the edge?
    Nothing? Then space (referring to space as a place with nothing occupying the space) is kinda nothing, so why would there be a finite space? This is beyond most of us. There is no real fact to answer this question.

    Good luck on finding a straight answer
  12. Jan 16, 2014 #11
    A real sphere is a three-dimensional object. The surface of a sphere also occupies three dimensions. You cannot avoid this characteristic simply by refusing to admit it.
  13. Jan 16, 2014 #12


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    The surface is 2-dimensional, which is how come you can uniquely specify a location on the Earth with only two numbers, latitude and longitude. You can embed a sphere in 3d space and use it to describe the surface of a collection of atoms and describe locations with (x,y,z) co-ordinates plus the constraint that ##x^2+y^2+z^2=r^2## if you wish. But it's important to realise that you've added something over and above the curved 2d structure that jedishrfu is talking about.
  14. Jan 16, 2014 #13
    The surface certainly occupies 2 dimensions, not three.
  15. Jan 16, 2014 #14
    Only object can have dimensions, nothingness that we called "space" can't have any dimensions. Infinite is an adjective so it only applies to object and we know, that no object can be infinite because object have shape. Thus, space is not finite or infinite and nothingness can't be finite or infinite because nothing is nothing. Btw, this is just my opinion.
  16. Jan 16, 2014 #15
    I think I agree with your statement. Only object can have dimension, while space, as we know is nothing because it is shapeless and dimensionless. I am confused, why most people still saying that it is possible that space is finite but yet unbounded.:confused:
  17. Jan 16, 2014 #16


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    So in other words, considering that you don't have a good grasp on topology, you are going to contradict the prevailing view of cosmologist based on just your "opinion"?

    Several people have provided elementary topological examples on how something can be finite and yet unbounded. I am not sure how you are able to ignore those and continue to hold your opinion, especially when it is not based on any solid mathematical framework.

    We welcome questions when you don't understand something, which was fine at the start of this thread. However, you now seem to be entrenched in your opinion despite responses to the contrary. Producing an idea based simply on your "opinion" and without any solid justification is considered to be a speculative post, which is prohibited by the forum rules that you had agreed to. Therefore, this thread is done.

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